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BIOL211.CH14
CH14: DNA and the Gene
Question | Answer |
---|---|
The region at the end of a linear, eukaryotic chromosome is called a _________. | 14.4 telomere |
During each chromosome replication, single-stranded DNA shortens by 50-100 deoxyribonucleotides. Why? | 14.4 on the lagging strand, DNA polymerase III cannot add DNA because there is not enough room for the primase to add a RNA primer. Single stranded DNA results at the tip and degrades. |
Do bacteria and archaea DNA shorten during replication? Why or why not? | 14.4 bacteria and archea have circular chromosomes, so do not have telomeres and the shortening problem. |
The function of the enzyme telomerase in telomere replication is: | 14.4 to prevent shortening of telomeres by adding a RNA primer to the lagging strand. |
At a telomere, the lagging strand is missing DNA. Does this strand end in 3' or 5'? | 14.4 The lagging strand ends in 3'. If DNA synthesis must occur in the 5'->3' direction, it needs an RNA primer. Telomerase adds this primer. |
Does telomerase exist in somatic cells? | 14.4 No - only in reproductive organ cells that will undergo meiosis to produce gametes. Chromosomes of somatic cells gradually shorten with mitotic divisions. |
This enzyme "proofreads" by excising incorrectly added bases during DNA synthesis. | 14.4 DNA polymerase III (in prokaryotes) DNA polymerase (in eukaryotes) |
A kink-shaped defect in DNA caused by exposure to UV light is caused by a _____. | 14.4 thymine dimer: a thymine-thymine pair that stalls DNA replication and transcription enzymes, leading to cell death. |
This activity repairs defective nucleotide bases after DNA synthesis is complete (compared to proofreading which happens during synthesis). | 14.4 nucleotide excision repair. |
People with the rare hereditary disease _____ have defective DNA excision repair systems. Their skin develops lesions with the slightest exposure to sunlight. | 14.4 XP (xeroderma pigmentosum): sufferers are extremely sensitive to UV light. |
a population of genetically identical individuals is called a _______ | 14.1 a strain |
define virulence | 14.1 ability to cause disease and death |
a liquid or solid that is suitable for growing cells is a ____. A collection of cells that grows under controlled conditions is a ____. | 14.1 medium; culture |
Avery et al.'s experiment showed that the "transforming factor" consisted of ___. (protein, RNA or DNA). | 14.1 DNA is the transforming factor. |
The Hershey-Chase experiment showed the virus coats consist of ____ and viral genes consist of ____. | 14.1: virus coats consist of protein; viral genes consist of DNA |
In the Hershey-Chase experiment, the hypothesis that virus coats consist of protein radiactively tagged viral protein, agitated the culture and centrifuged in a test tube. Was the viral protein in the solution or tip? | 14.1 The radioactive viral protein was removed from cells by agitating the solution, then it remained the solution, NOT at the tip of the test tube. (DNA was in the pellet at the tip). |
Monomers that polymerize to form DNA are called ____. | 14.2 deoxyribonucleotides. |
Draw the primary structure of DNA, showing where the 5' end is and where the 3' end is. | Your drawing should look like 14.3/Figure 14.6. |
DNA replication is semiconservative, conservative, or dispersive? | 14.2: semiconservative: each newly made DNA molecule comprises one old and one new strand. |
This model of DNA replication predicts that Generation 1 will be 1:1 15N:14N; Gen 2 will be 1:3 15N:14N. | 14.2: Conservative replication: parental strands stay intact and daughter strands are entirely new. |
In the DNA Synthesis reaction, the ___ monomer is added to a DNA polymer when a phosphodiester bond forms between the 3' carbon at the end of the DNA strand and the 5' carbon on this monomer. | 14.2 dNTP (deoxynucleotide triphosphate). |
Eukaryotic chromosomes are linear and have multiple "points of origin". What shape are bacterial chromosomes and how many points of origin do they have? | 14.3 bacterial chromosomes are circular and have a single point of origin. |
DNA polymerase I and DNA ligase work on the leading strand, the lagging strand, or both? | 14.3 p.307: DNA polymerase I and DNA ligase work on the lagging strand. |
In DNA synthesis on the lagging strand, Okazaki fragements are synthesized by enzymes ____ and ______. | 14.3 Primase (catalizes the synthesis of an RNA primer) and DNA Polymerase III (extends the fragment) |
This enzyme catalyzes the breaking of hydrogen bonds between base pairs, which opens the DNA double helix. | 14.3 helicase. It works on both the leading and lagging strands. |
These proteins keep the strands separated by helicase from rejoining. | 14.3 SSBPs (single-strand DNA binding proteins). |
What does enzyme topoisomerase do? | 14.3 undoes the twists and knots downstream of the DNA replication fork by cutting and rejoining DNA |
In the leading strand, DNA is synthesized in the 5'->3' direction. What direction is it synthesized in the lagging strand? | 14.3 DNA is synthesized in the 5'->3' direction in BOTH the leading and lagging strands. In the lagging strand, this means that Okazaki fragments will form. |
What enzyme catalyzes joining of Okazaki fragments into a continuous strand? | 14.3 DNA ligase. |
What does the "sliding clamp" do? | 14.3 It holds DNA polymerase in place during strand extension |
At the telomeres in eukaryotic chromosomes, what enzymes act after telomerase binds to the "overhang" to continue DNA synthesis? | 14.4 Primase, DNA polymerase, and ligase synthesize the lagging strand. |